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Rogue Leader
02-03-2011, 12:08 AM
So when I rebuilt the engine last year I also rebuilt the carb. It ran good up the alcan but after a month or so it wouldn't idle without the choke partially pulled (like 1/8th total pull or so). I've played with the idle mixture screw but that doesn't have an any affect on it. I also experience a stuck/frozen throttle on those cold days -10 or below. it runs fine while at speed I can push the choke all the way in but if i pop it out of gear it almost instantly dies, which takes the brakes with it. I've been experiencing a loss of gas milage and it seems to run hotter than normal. Should I try to rebuild the carb again? It's the stock carb.

Sean

subzali
02-03-2011, 08:04 AM
Have you checked for vacuum leaks?

DenCo40
02-03-2011, 08:05 AM
If it's the stock Aisin, have you check the idle cutoff solenoid? I had a problem last year that was similar to what you describe. Also may want to verify all linkage moves freely and returns to normal stops with just the springs holding it.

RicardoJM
02-03-2011, 08:19 AM
Sorry to hear about the issues you are having. Are the idle issues occurring upon start up (when the engine is cold/warming) and once at operating temperature? In reading your post, it sound like this is the case. I've had some Idle issues with my Aisan carbs and have been able to get them sorted out. With all the experience on this Forum (and MUD if we need it) you'll get issue addressed.

The carb's idle circuits are designed to mix fuel and air to achieve a ratio. Your "work around" for the idle issue is to decrease the amount of air, i.e. partially choke. Based upon that, one of the first things to check is where the "excess" air is coming from. Typically it is coming from a small gap where;

the carb fits to the carb base
the carb base fits to the intake manifold
the intake manifold fits to the head


To check these areas, spray/spritz some break cleaner at each area and then listen for a change in idle. When the idle changes, you have found an issue that needs to be addressed. To get a feel for what the change sounds like - do a spritz at the intake to the air cleaner and wait a bit. It doesn't take a bunch of brake cleaner to change the idle and you need to be methodical and patient. If you spray everything quickly and then the idle changes - you won't know where the air leak is.

The "excess" air can also come from;

Holes in the vacuum hoses connected to the carb base (for the PCV valve) and intake manifold (brake booster and transfer case shifter)
Tear in the brake booster
Tear in vacuum transfer case shifter innards
a crack in the bottom of the intake manifold (typically occurs on newer rigs, not so much on our early rigs)


To check (most of) these items, connect a vacuum pump to the end of the vacuum hose that connects to the carb base or manifold. Pump the vacuum unit up to create a vacuum and then let it sit for some time to see if the vacuum decreases. If it decreases, it indicates an issue that needs to be addressed.

Are you running a header or the stock exhaust manifold?

For your idle issue, I would recommend starting with the above diagnostics. If that all checks out. The next component to check is the idle cutoff solenoid. If that checks out, we can then move on to the carb itself. What altitude are you at?

subzali
02-03-2011, 08:24 AM
...
the intake manifold fits to the head

...

Fixed it for you Ricardo :D

Good post :thumb:

RicardoJM
02-03-2011, 08:33 AM
Fixed it for you Ricardo :D

Good post :thumb:

You are correct:D. I made the edit.

Rogue Leader
02-03-2011, 12:57 PM
All the problems aren't affected by the engine temp. It looks like my PCV is bad, theres oil leaking all around it and when I pulled the carb off there was a white milky substance that looked like aerated oil. the linkage moves freely when not cold, I think there might be some grease or the like that is freezing at the low temps.

RicardoJM
02-03-2011, 01:28 PM
It looks like my PCV is bad, theres oil leaking all around it and when I pulled the carb off there was a white milky substance that looked like aerated oil.

This should not be occurring but is consistent with a vacuum leak being the cause of your idle issue. That is to say, it seems like the PCV hose is damaged and allowing oil to get into the hose - when the engine is running vacuum is pulling oil through that hose and into your intake manifold and causing the white milky substance. That same hole would create a vacuum leak that is the source for the "excess" air. All things being equal, I would get a new PCV valve, grommet and hose put in place and see if the idle issue improves.

It is still worth checking for other air leaks to confirm there are not any others.

Rogue Leader
02-08-2011, 07:32 PM
Installed a new PCV valve, gasket and hose. It's weird that the port on my carb base and the PCV Valve are different sizes, the hose fit perfectly at the PCV but its too small for the carb base. I soaked it in hot water and got it to fit on enough to put a hose clamp on it. I found 2 vac leaks, one the hose had fallen out, the other the nail that used to plug it up was missing so I put another one in. It ran fine for several miles after warming up but then the old problems persisted ie dying when i took it out of gear. It was also running unusually hot. We played around with the idle mixture screw and it didn't change anything no matter how much we turned it.

subzali
02-08-2011, 09:56 PM
One thing that happened to me for a time was when I took it out of gear or idled up to a stop my engine would die. I found a bunch of floaties in the carb bowl. Once I cleaned them out the problem went away. It's easy to check.

The idle mixture will only affect the idle mixture, it doesn't have any real effect once you're into the main and/or secondary circuits.

Running hot can sometimes be an indication of a lean mixture. Again check for vacuum leaks. Also, pull your plugs and check their condition, that's an easy way to tell how your mixture is looking. If they're anything but tan colored you've got issues you need to address.

Another test for vaccum leaks is to pull off your brake booster hose (while the engine is running) and put your finger over the port on the intake manifold and see if the situation improves. Sometimes a leaking brake booster diaphragm will leak excess air into cylinders 5 and 6 and cause them to run lean. In some cases when you press on the brake pedal the excess air is enough to kill the engine (from what I've heard of other experiences).

Also it would be good to check your timing, just to make sure there is nothing going wacky there. Having it too far advanced or too far retarded can have an effect on engine temperature as well.

Just some quick easy diagnostics to check.

RicardoJM
02-09-2011, 07:27 AM
You are definitely in better shape by addressing the vacuum leaks:thumb:. It was not clear if you checked the brake booster and vacuum shift for leaks - did you check these?

The engine dieing could be your idle cutoff solenoid is acting up. It is easy to test the solenoid. Get a jumper on the end of the wire and hook touch it to power. It should click. The solenoid gets power when the key is in the run position. The click you hear is the pin retracting and opening up the idle circuit for fuel to flow through. They don't often go bad, and might be the wire providing power has a kink or splice that is failing intermittently. We had that issue on the wiring in TheBoomBoom's rig. He had similar issues with idle and the engine dieing.

Rogue Leader
02-09-2011, 02:13 PM
Where's the vacuum shift hoobie doobie located at? I'll check the brake booster and the idle solenoid when I get home.

RicardoJM
02-09-2011, 02:33 PM
Where's the vacuum shift hoobie doobie located at? I'll check the brake booster and the idle solenoid when I get home.

On your intake manifold there will be a vacuum hose that goes to a metal tube on the firewall near the top. That metal tube goes to a small box on the passenger side of the firewall. The other thing going into that box is the cable that runs to the 4D knob in the truck. The knob in the truck is a toggle for the small box. Knob in, the box directs vacuum to put t-case in 2WD; knob out the box directs vacuum to put t-case in 4WD. Of course coming out of that box are two tubes, one for each circuit.

To test apply vacuum pump to the hose where it connects to the manifold. It should hold the vacuum. Then pull the knob out and confirm that it still holds vacuum.

Rogue Leader
02-10-2011, 01:22 AM
I've got a manual linkage for my xfer case. I've got that hole on the manifold plugged.

RicardoJM
02-10-2011, 07:58 AM
I've got a manual linkage for my xfer case. I've got that hole on the manifold plugged.

Well then, we can safely rule out a leak in the vacuum shift system:D.

Whats the word on the idle solenoid and brake booster checks?

nattybumppo
02-10-2011, 08:15 AM
FWIW...if you have an EGR system, check to make sure any filter that is on it is clean and functioning properly. This paper and gauze filter caused all sorts of havoc on my 60 until we cleaned it out.

rover67
02-10-2011, 10:27 AM
I've had the EGR valve on my 40 (2f with stock emissions) stick open and cause issues. I just undid the vacuum line going to it and pulled a vacuum on the valve and let it snap shut a few times. seemed to fix it.

Rogue Leader
02-10-2011, 11:33 AM
The idle solenoid is funky. It works but only if I manually push the pin in several times before hooking it up to the battery. Once I pulled it off the battery and tried again it wouldnt work. The wiring is good, just seems like the solenoid's innards are gummed up a bit

RicardoJM
02-10-2011, 12:19 PM
The idle solenoid is funky. It works but only if I manually push the pin in several times before hooking it up to the battery. Once I pulled it off the battery and tried again it wouldnt work. The wiring is good, just seems like the solenoid's innards are gummed up a bit

Well that would be consistent with the issue you are experiencing:thumb:.

I don't know that it is a serviceable part that you can take apart and clean up. I would think Mark's Offroad might have a replacement one that you could get. You might also post up in the Wanted section to see if someone has one in their stash/spares. The connector end of these did change a bit over the years, if the one you get does not have the matching connector you could just splice in new connectors. IIRC, your carb is the DD38 that was used from 69 through 74 which is compatible with a "bent needle" solenoid in my spares stash. You are welcome to it, but I don't know if it is reasonable to expect that the needle can be bent straight and work without issue for the long term.

Being that it is sticking and not good, you might try shooting some carb cleaner up into the body and see if it will clear the stickiness. Of course not knowing what it looks like inside it could hasten its death.

subzali
02-10-2011, 01:31 PM
Ricardo, I think technically that should be DD38/38, so you can designate both throttle plate sizes. But that is neither here nor there...:D

Sean, it would probably be worth checking your idle solenoid. The only serviceable part is the o-ring that goes on it. It may have disintegrated and possibly got pieces lodged in the idle circuit somewhere. If the valve itself is bad, then as Ricardo mentioned you will probably have to find one elsewhere. But do make sure it is getting good clean power though. If there is a problem with it getting consistent power then that needs to be addressed or else you will never be able to get it to really run right.

RicardoJM
02-10-2011, 01:51 PM
Ricardo, I think technically that should be DD38/38, so you can designate both throttle plate sizes. But that is neither here nor there...:D
Yeah, I could have it wrong from the technical name.

Sean, it would probably be worth checking your idle solenoid. The only serviceable part is the o-ring that goes on it. It may have disintegrated and possibly got pieces lodged in the idle circuit somewhere.
If Sean's carb is the DD38/38 the idle cutoff solenoid does not have an o-ring. The o-ring came into play on later carbs.:thumb:

subzali
02-10-2011, 04:05 PM
well, that goes to show you that two heads are better than one! :homer: :D

Jacket
02-10-2011, 04:15 PM
^Which one of you is Homer?

Uncle Ben
02-10-2011, 04:25 PM
^Which one of you is Homer?

Which one is Gomer?

corsair23
02-10-2011, 05:50 PM
Ricardo always seem to be smiling so that must make Radar, Homer right? :lmao:

subzali
02-10-2011, 07:18 PM
I've got two alter egos :rolleyes: :homer: